#btn1 {
    color: yellow;
    background-color: currentColor;
}

#btn2 {
    color: red;
    background-color: currentColor;
}

.btn {
    width: 100px;
    height: 50px;
    border: 0;
    font-size: 18px;
    border-radius: 8px;
}

span {
    filter: grayscale(1) contrast(999) invert(1);
}

/*
body {
    filter: grayscale(100%);
    !*网站全灰色*!
}*/
